You may not feel like agreeing with your ex about anything after a divorce. However, when it comes to child custody and parenting plans, it is easiest if you both agree on how things are going to be done. The children will behave better if they have the same rules everywhere.
For example, it's dangerous for one parent to always be strict and for the other parent to be the "fun" one. A father who only sees his kids on the weekends may be focused only on making sure that they like him, for instance. He won't make them do homework, he'll let them watch TV and eat as many snacks as they want, he won't have a bedtime for them, and they'll basically be free to do what they desire. The kids, of course, will love this.
The problem, though, is that this massively undercuts the other parent's position. In this example, the mother may have a very hard time getting the kids to do their homework and go to bed on time. She'll feel that she can't control them, and they'll be angry when they're with her because they just want to have fun.
This set-up does not help with the children's growth and development. It is not healthy for them or the parents. Their grades can suffer in school and their relationships will suffer at home.
If you're really putting your kids first, you want to get a parenting plan in place and stick to it. When both parents work together, it helps the children in every area of their lives. Be sure you know how a legal parenting plan can be set up and how it fits within your custody agreement in California.
Source: Empowering Parents, "The Disneyland Daddy," James Lehman, accessed Oct. 06, 2016